1. Field
Exemplary embodiments of the present invention relate to a wireless communication system, and more particularly to a method and an apparatus for allocating a Channel State Information-Reference Signal (CSI-RS) between cells in a wireless communication system.
2. Discussion of the Background
With the development of communication systems, consumers, including business companies and individuals, require wireless communication terminals supporting various services.
Current mobile communication systems, such as 3GPP (3rd Generation Partnership Project), LTE (Long Term Evolution), and LTE-A (LTE Advanced), are resulting in the development of technology for a high-speed large-capacity communication system, which can transmit or receive various data, such as images and wireless data, beyond the capability of providing a voice service, and can transmit data of such a large capacity as that transmitted in a wired communication network. Moreover, the current mobile communication systems require a proper error detection scheme, which can decrease the reduction of information loss and improve the system transmission efficiency, thereby improving the system performance.
Further, for the current wide variety of communication systems, various reference signals have been and are being proposed in order to provide counterpart apparatuses with information on a communication environment, etc., through a downlink or an uplink.
For example, in the LTE system, a Cell-specific Reference Signal (CRS), which is a reference signal, is transmitted at each sub-frame.
At this time, since the maximum number of antenna ports supportable in the downlink of the LTE system is four, CRSs are allocated to and transmitted through a maximum of four antennas according to the time/frequency.
Meanwhile, the next generation communication technologies, such as the LTE-A, which is being currently developed, can support a maximum of eight antennas. Therefore, the current CRSs defined for only four existing antennas are insufficient for detection of channel information at the time of downlink transmission. To this end, a technology for obtaining channel state information of a maximum of eight antennas by newly defining a reference signal named “Channel State Information-Reference Signal (CSI-RS)” is being discussed.
In other words, a communication system using a maximum of eight Multiple Input Multiple Output (MIMO) antennas at each of the transmission port and the reception port is being discussed, and a scheme of transmitting CSI-RSs discriminated according to the antenna ports or antenna layers for the transmission or reception thereof is being discussed. However, up to the present, only basic definitions for the CSI-RS and definitions for the overhead problem have been arranged, and definitions for CSI-RS allocation and transmission have not been arranged. In this regard, the next generation wireless communication systems are requiring a specific scheme for the CSI-RS allocation and transmission.